1. Field of the Invention
The present invention generally relates to laser scanning systems and, more particularly, to laser scanning apparatus and methods of evaluating and validating bar code symbols such as Universal Product Code (UPC) symbols, and the many other types of symbols currently in use. More particularily the invention relates to a laser bar code reader having a focused elliptical field of view.
2. Description of the Invention
The grocery and food processing industries have developed a universal product code to uniquely designate each assigned product with a series of lines and spaces of varying widths, which pattern decodes to a multiple digit representation. Each such pattern is printed on the labels of even small items, and each line of the pattern must therefore be printed with a high degree of graphic precision.
The graphic arts industry has had considerable difficulty in printing the labels and packaging on a mass production basis due to the necessity of having to print the lines with the appropriate widths and against the appropiate background color. In view of the high production rates involved for grocery products, and other industrial products, poor quality control over the line widths and over the color contrast between the the line color and the background color results in a loss of considerable stock.
Other than the fixed scanning systems built into checkout counters of supermarkets, the prior art has proposed laser scanning heads moveable relative to, and electrically connected, with a console. However the known laser systems have not proven to be satisfactory. One of the reasons for the unsatisfactory results from the use of prior art scanning devices is that such laser scanning devices used a laser light source which was round in shape. The bar measurements taken by the scanning head were subject to a considerable amount of noise and modulation, thereby leading to inaccurate measurement evaluation and possible decoding errors. Finally, other ease of operation and evaluations criteria desired by the graphic arts industry have not been embodied in a laser scanning system.